1. Field of the Invention
This invention relates to improvements in blade type fountain coaters especially suitable for applying coating materials to paper webs, and more particularly concerns a novel metering device for such coaters.
2. Description of the Prior Art
Coating apparatus of the type with which the present invention is concerned is particularly adapted for so-called short or zero dwell coating, attaining maximum transfer of coating material from a suspension onto the surface of a continuously running web, with minimum or virtually no soaking of the material into the body of the web. Basic principles of such apparatus have been disclosed in Neubauer U.S. Pat. No. 3,348,526. According to that patent, which is incorporated herein by reference for a more detailed explanation of the underlying principles, coating material is supplied to and along a coating nip of a generally upwardly projecting doctor blade extending across the width of a web travelling continuously on backing surface means such as a roll.
A more recent Damrau et al U.S. Pat. No. 4,250,211 discloses various alleged improvements on the apparatus first disclosed in the aforesaid U.S. Pat. No. 3,348,526. Among the expedients in the more recent patent, is an arrangement whereby a partially enclosed coating chamber or pond converges toward a coating nip defined by and between an upstanding doctor blade, and an upstanding, slidably adjustable orifice plate has an upper edge which defines a metering orifice slot for controlling back pressure in the coating application chamber pond. In one form, the orifice plate is secured adjustably by screws which extend through slots in the plate. In another form the plate is slidably adjustable by manipulation of various screw jack devices. These prior arrangements lack convenience and in certain aspects are complicated and cumbersome.